SN 1987A, a peculiar variant of SNe II-P, is described
extensively in many other reviews (see
Section 1); it is mentioned here only
briefly. In general, its spectral evolution resembled that of SN 1992H
(Figure 12), as can be seen,
for example, in
Menzies (1991).
Jeffery & Branch
(1990)
presented an analysis that showed that to a considerable extent the
evolution
of the line spectrum during the first 100 days could be understood on the
basis of simplifying assumptions such as resonant-scattering line source
functions and LTE line optical depths. One important aspect of the SN 1987A spectrum is that narrow emission lines from
the circumstellar ring were present
(Wampler &
Richichi 1989), and these became dominant at
3 years
Wang et al 1996).

Danziger et al
(1988)
found that around day 530, the peaks of several emission lines (most
notably [O I] 6300, 6364) shifted
rapidly to bluer wavelengths. This was probably due to the formation of
dust in the ejecta
(Lucy et al 1991),
which is consistent with the nearly simultaneous increase in the decline
rate of the optical light curves and the rapid growth of an IR excess. The
lines remained blueshifted even in the very late-time spectra obtained with
the Hubble Space Telescope ( 2000 days;
Wang et al 1996),
which shows that the dust was still present.

The optical spectra of SN 1987A provide considerable
evidence for the formation of clumps and mixing of different layers in the
ejecta, as had already been deduced from other studies (e.g. X-ray emission;
Arnett et al 1989,
and references therein). 1. Very early,
Hanuschik &
Dachs (1987; see also
Phillips &
Heathcote 1989)
drew attention to the "Bochum event," an asymmetry in the
H and other
hydrogen-line profiles. One possibility is that a blob of
Ni56 was ejected asymmetrically
(Chugai 1992,
Utrobin et al
1995). 2.
Stathakis et al
(1991) showed that the [O I]
6300, 6364 profile was
serrated in a manner similar to that found for SN 1985F by
Filippenko &
Sargent (1989), with FWHM typically 80 km s-1
for the emission-line peaks. The interpretation is that the [O I]-emitting
material is clumpy, probably owing to the formation of Rayleigh-Taylor
instabilities at the boundary of the oxygen-rich and helium-rich layers.
Chugai (1994a)
estimated the mass of clumpy oxygen to be 1.2-1.5
M.
3. Hanuschik et al
(1993)
showed that the H
profile exhibited peaks with a somewhat larger velocity scale: FWHM =
160-400 km s-1. Subsequently,
Spyromilio et al
(1993)
demonstrated that at least one of the
H clumps was also
visible in the [Ca II] 7291, 7324 and [Fe II]
7155 emission lines,
directly demonstrating that small-scale mixing of hydrogen and
radioactive products occurred in the ejecta.